The epidemiology of abdominal aortic diameter

The diameter of the abdominal aorta is central to the diagnosis of abdominal aortic aneurysm. This study aimed to determine the associations between the diameter of the abdominal aorta at three distinct locations and the traditional cardiovascular disease risk factors as well as calcified atherosclerosis.

A total of 504 patients (41% women) underwent whole body scanning by electron beam computed tomography (EBCT) and a standardized assessment for cardiovascular disease risk factors. The resulting EBCT images were retrospectively interrogated for the diameter of the abdominal aorta just inferior to the superior mesenteric artery (SMA), just superior to the aortic bifurcation, and at the midpoint between the SMA and bifurcation.

Mean patient age was 57.8 years. The mean (SD) diameter was 21.3 (2.9) mm at the SMA, 19.3 (2.5) mm at the midpoint, and 18.6 (2.2) mm at the bifurcation. In a model containing the traditional cardiovascular disease risk factors, age (standardized beta = 0.96), male sex (beta = 3.06), and body mass index (standardized beta = 0.68) were significantly associated with increasing aortic diameter at the SMA (P < .01 for all). The significance of the associations for these variables was the same for aortic diameter at the midpoint and bifurcation. Furthermore, a 1-unit increment in the calcium score in the abdominal aorta and iliac arteries was associated with 0.13-mm (P < .01) and 0.09-mm (P = .02) increases, respectively, in aortic diameter at the SMA. The results were similar for the midpoint (beta = 0.19, P < .01; beta = 0.12, P = .01, respectively) and bifurcation (beta = 0.09, P < .04; beta = 0.09, P = .03, respectively).

Age, sex, body mass index, and the presence and extent of calcified atherosclerosis in both the abdominal aorta and iliac arteries are significantly associated with increasing aortic diameter independent of the other cardiovascular disease risk factors.